The chances of a large flare happening on that day are pretty high in my opinion, but not because of anything Geryl says. The sun has been coughing out M and X class flares for fun recently and there has been a lot of associated CME's. Looking at the sun right now, it's still peppered with spots, although they all seem to be either decaying or fairly stable.
Keep in mind that C class flares happen all the time, so let me make a little prediction of my own. I predict that on this day, the sun will unleash several C flares. I also predict that any activity on the sun at all, will be hailed as "spot on" by Geryl. He's been utterly wrong thus far, he waits until after the date, checks whatever activity has happened on the sun, then claims he predicted it. It's pathetic, but the worst part is that people actually take him seriously.
Edit: Here is what his page says about this prediction:
Between July 14 and 17, 2011 we also expect a complex eruption as the extraordinary August 1, 2010 event on the Sun…! If not… then October 10-11-12-13 is the next date…
Ok, so there was no flare activity whatsoever between July 14th and 17th. So a "complex eruption" will take place on one of these dates on October. The "extraordinary" event which happened on August 1st 2010 was actually nothing more than a C class flare. As I stated above, C flares happen constantly, there are usually several per day. So this new "prediction" is saying that a C class flare will happen some time in a four day period. Wow, astonishing!! To the OP, where did you read about him predicting "a flare of Maya strength of over 200 or in nanateslas scale, over 200 or so." I see nothing on his site about this, just this "complex eruption" garbage?